Shipping Rate Calculator Overview Showing real-time shipping rates at checkout — from UPS, FedEx, USPS, DHL — lets customers choose their preferred service and prevents you from under- or overcharging for shipping. Every major platform supports carrier-calculated rates natively or through apps, and a multi-carrier rate shopping tool can save you 15–40% on shipping costs by automatically selecting the cheapest option. When to Use This Skill - When adding real-time carrier rate quotes to checkout - When building a multi-carrier shipping rate comparison feature - When implementing free shipping…